Essentialism

The concept of Essentialism states that there are innate, essential differences between men and women. That is, we are born with certain traits. This is often used as an explanation for why there are so few women in science and technology. It is also used as a rationale for pigeonholing, offering limited education, hiring discrimination, etc. It is also sometimes raised (including by women) under the guise of Equal but different.

Biologically essential differences between men and women's skills and social behaviour — or at least those of men as a group and women as a group — are the subject of active research. The strength of the findings of this research is often exaggerated when repeated, both by the media and by individuals. It is also common to find people in informal situations implying that a difference in the mean or median performance of men and women implies that any individual man will have that same difference from any individual woman.

In recent times, advocates of Sociobiology and Evolutionary psychology often claim evolved genetic differences between the brains of men and women as the source of behavioral differences in society.

Essentialism and transphobia

Often, essentialism supports and is supported by transphobia, as essentialists claim that a person's sex is the sex they were coercively assigned at birth (often mischaracterizing this sociological sex assignment as "biological"). It's common for essentialists to claim that trans people's genders and sexes are less valid than cis people's genders and sexes, by using irrelevant scientific facts like the unchangeability of chromosomes to lend their arguments scientific legitimacy. In this case, essentialists support a double standard that involves using a trans person's karyotype to undermine their innate sex and gender, while never asking that a cis person be karyotyped to confirm that they are the gender and sex they say they are. A related form of essentialism is the use of "male socialization" to insinuate that trans women are really men, while refusing to acknowledge narratives from trans women that show that many trans women were never fully recognized as male and absorbed the same social programming that girls and women do.

Misuse of science and misunderstanding of socialization are both seen in (but not limited to) the writing of trans-excluding radical feminists.

"Parents and teachers persist in thinking boys are simply better at math, said Janet Hyde, the University of Wisconsin-Madison researcher who led the study. And girls who grow up believing it wind up avoiding harder math classes."